Screening and economics.

Screening for disease involves expenditure now in order to reap benefits in the future. It is important to understand why future benefits should be discounted in the cost-benefit calculation. The reasons are derived from a societal preference for consumption now over consumption tomorrow, combined with the productivity of capital, which enables goods today to be transformed into more goods tomorrow. It is also necessary to put costs and values on human lives. This is simplified at present in the UK because a highly restrictive immigration policy implies that the net value of the average additional citizen is zero (or even negative). The cost-benefit calculations that are presented must be carried out highly systematically in order to avoid double counting or omission. A computerized spreadsheet is ideal for this purpose.